The invention relates generally to the field of curable compositions for forming an insulating material, as well as the insulating material itself, as used for example in refractory or refrigeration constructions. In particular, the invention relates to the field of such compositions where the resulting material is a block or panel comprised of crushed pumice and type S mortar, and preferably additional fillers or additives.
For ultra-high temperature or ultra-low temperature applications, special construction materials must be used. Many of the normal construction materials such as wood, metal, concrete block or brick are not suitable for such applications. It is necessary to provide a material whose composition enables it to withstand the extreme temperatures. Many such materials are known in the industry. For example, it is well known to use refractory blocks or bricks in fireplace or furnace constructions. These materials have both high temperature resistance and high strength.
A composition which has proven to be successful in these applications includes the use of crushed pumice as an aggregate filler. Pumice is a volcanic stone which is strong yet lightweight. A cubic foot can weigh as little as 24 to 30 pounds, due to the presence of numerous sealed air chambers and pockets within the individual stones. Crushed pumice can range in size from pieces three-quarter inches in diameter to that of a grain of sand. Pumice will actually float in water. Prior to this invention, the pumice has always been mixed with portland cement and formed into blocks, panels or bricks. Portland cement is an hydraulic cement produced by pulverizing clinker consisting essentially of hydraulic calcium silicates, usually containing one or more forms of calcium sulfate as an interground addition. The pumice allows for a block roughly one-third lighter in weight than a block of conventional concrete. The pumice block has high insulation properties due to the entrapped air chambers, and is therefor ideally suited for extreme temperature applications.
To be used in fireplace constructions, pumice block must meet minimum standards regarding both compressive strengths and heat penetration. Additionally, the blocks must be able to withstand long-term and repeated high temperature situations without suffering degradation or deterioration. As it is desirable in construction to minimize the amount, size and weight of construction materials, while still meeting the structural requirements and standards, experimentation is ongoing to develop improved construction compositions utilizing pumice.
It has been discovered that pumice panels or blocks having improved structural and temperature insulation properties can be formed of a new composition as described in U.S. Pat. No. 5,017,232, issued May 21, 1991 to this inventor. The pumice blocks of the new composition allow for the use of thinner blocks than those required under the old composition, while providing increased temperature insulation, higher compressive strengths and lesser degradation under long-term conditions.
That composition comprises the combination of pumice, type S mortar, and glass fibers, which when mixed with water form a hard material after curing. Type S mortar is a specialty masonry cement normally used to join and set bricks or concrete blocks. The type S designation is a standard used in the industry, and certifies that the product meets the required ASTM specifications. The composition can be formed into blocks, panels or bricks of various shapes and sizes for use in construction.
It has now been discovered that certain additives and fillers are compatible with this composition, and provide the finished product with improved properties with regard to temperature parameters, weight and impact resistance. It has also been discovered that for certain use the glass fibers can be left out of the original composition.